1. Field of the Invention
The present invention relates generally to a housing for a centrifugal fan, blower or the like. More particularly, the present invention relates to a volute housing for a centrifugal fan, blower or the like which reduces noise generated during operation.
2. Disclosure Information
Centrifugal fans or blowers are commonly used in the automotive, air handling and ventilation industries for directing a forced flow of air through a variety of air conditioning components. In a typical centrifugal blower, air is drawn into a housing through an aperture by a rotating blower or fan. This air is then forced around the housing and out an air exit end. In some situations, an undesirable whistling or other tonal noise may be generated by this flow of air. (As used herein, tonal noise means noise at frequencies equal to (nBN/60) where n equals 1, 2, 3, . . . , B equals the number of blades on the fan wheel and N is the rotational speed per minute of the fan wheel.) This noise is primarily due to a pressure pulse generated when fan blades pass the blower cut-off region, the necked down portion immediately adjacent the exit end of the blower housing. Various modifications to the housing have been proposed for reducing this noise.
The most common method for reducing this noise has been to modify the shape of the cut-off region of the blower. This has been done by inclining or altering the sides of the housing in this region, to effectively reduce the sudden increase in pressure (pulse shape) when rotating blades pass the cut-off region. More gradual cut-off inclinations are required for tonal noise reductions but these may affect airflow performance and manufacturability of the housing and its assembly.
Therefore, it would be desirable to reduce the tonal noise generated by a centrifugal blower without affecting its performance. It is an object of the present invention to reduce tonal noise in an economical manner without affecting the performance of the blower.